The prior art construction and use of composite wall panels is perhaps best exemplified by the disclosure of U.S. Pat. No. 3,310,926. The frame members for such wall panels are normally extruded from a metallic substance such as aluminum to provide a light weight, yet strong, frame that will impart structural integrity to the resulting panel. The facing, or skin, of such panels is also a preferably light weight material, such as a plastic sheeting material or a thin gauge metallic substance (in this situation, as well, aluminum may be satisfactorily employed). The frame members have historically been fastened together by suitable means such as rivets, bolts or other mechanical fasteners, and the facing materials have historically been secured to the frame members by an adhesive. The interior, or core, of each panel is usually filled with thermal, as well as sound, insulating materials. Typical core filler materials are polystyrene, or other plastic foams, fiberglass layers and even phenolic impregnated paper honeycomb sheets. In fact, virtually any type of core filler may be employed, so long as it provides the desired insulating qualities. Such panels are sufficiently rigid as to provide structural integrity to the walls constructed therefrom, and yet they are sufficiently light in weight that they can be manually manipulated with relative ease to facilitate the assembly and erection of walls in a building structure.
As is well known to the prior art, such panels may be erected upwardly of sill members supported from a foundation, roof or other relatively flat surface with considerable facility. The sill usually extends upwardly a sufficient extent so as to lie above the level of any water that would normally be expected to collect in proximity thereto. Doors, windows or other openings may be included, as desired or required. Even though such panels are frequently employed to erect structures that are preferably windowless, the panels are often required to be provided with openings to accommodate filters, duct work, louvers or the like.
Such panels are sufficiently air tight that they preclude the circulation of air therethrough, and the core material can be selected to prevent excess thermal conduction or radiation through the panels themselves. However, the material from which the frame members are normally constructed generally has rather high thermal conductivity. Because the surface area presented by the frame members is normally only a relatively small percentage of the overall surface area presented by the entire panel, the thermal loss occurring through the frame members themselves has been accepted as a necessary evil, and yet the cumulative heat loss by virtue of conduction through all the frame members in a building structure can be rather significant. As such, the thermal loss through the frame members has really been accepted only because there has not heretofore been an successful means by which to reduce, or eliminate, such losses.